• 대한기계학회논문집A
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• 제41권9호
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• pp.897-904
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• 2017

광학 탑재 장비는 다수의 광학 부품 및 검출기로 구성되며 목표물 탐지와 분류를 목적으로 항공기, 전차 및 군함에 탑재되어 운용된다. 수 km 고도에서 운용되는 항공용 광학 탑재 장비는 항공기에서 발생하는 진동 때문에 구조 안정성과 광학 성능 저하가 발생한다. 설계 단계에서 진동 환경조건에 대한 탑재 장비의 구조 안정성 및 광학 성능 검증이 요구된다. 본 연구에서는 진동 환경조건을 시험 표준 규격서와 항공기에서 발생하는 진동을 측정하여 분석하였다. 진동 환경조건은 구조 안정성 검증을 위한 내구도 진동조건과 광학 성능 검증을 위한 운용 진동조건으로 구분하였다. 구조 안정성을 고유진동수 해석, 내구도 진동 응답해석 및 정해석을 통해 검증하였다. 광학 성능을 운용 진동 응답해석 결과를 광학 설계/분석 프로그램에 적용하여 검증하였다.

• Geomechanics and Engineering
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• 제27권6호
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• pp.551-560
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• 2021

Due to the low strength and high compressibility characteristics, the loess deposits tunnels are prone to large deformations and collapse. An accurate stability evaluation for loess deposits is of considerable significance in deformation control and safety work during tunnel construction. 37 groups of representative data based on real loess deposits cases were adopted to establish the stability evaluation model for the tunnel project in Yan'an, China. Physical and mechanical indices, including water content, cohesion, internal friction angle, elastic modulus, and poisson ratio are selected as index system on the stability level of loess. The data set is randomly divided into 80% as the training set and 20% as the test set. Firstly, principal component analysis (PCA) is used to convert the five index system to three linearly independent principal components X1, X2 and X3. Then, the principal components were used as input vectors for probabilistic neural network (PNN) to map the nonlinear relationship between the index system and stability level of loess. Furthermore, Leave-One-Out cross validation was applied for the training set to find the suitable smoothing factor. At last, the established model with the target smoothing factor 0.04 was applied for the test set, and a 100% prediction accuracy rate was obtained. This intelligent classification method for loess deposits can be easily conducted, which has wide potential applications in evaluating loess deposits.

• Architectural research
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• 제20권3호
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• pp.65-73
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• 2018

The restoration of foundations supporting the immense load of the stone pagoda at Mireuksa Temple Site prioritizes securing its structural stability. But so far, rammed earth construction is still not easy to determine the structural stability. This paper aims to emphasize that a scientific experimental study was conducted on a rammed earth construction, to identify its methodology and obtain objective data about structural stability of the foundation work. An experimental study fabricated specimens from the soil that had been removed during the excavation survey, determined the allowable bearing capacity through plate load tests, and compared the results with the predicted stress after reassembly of the stone pagoda to estimate the structural stability. Then, the repair method was selected based on the experimental study result. The evaluation method of the restoration of foundations consisted of an examination of the allowable bearing capacity and settlement. The allowable bearing of the reinforced foundation was more than twice the contact pressure under the stacked stones of the pagoda. The possibility of settlement of the rammed earth foundation soil layer during the pagoda assembly is expected to be very low because the settlement amount of the reformed soil layer is less than half of the settlement of the stabilized existing soil layer.

• 대한인간공학회지
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• 제31권2호
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• pp.327-336
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• 2012

Objective: The purpose of this study is to find the problems of stability when people use the bassinet as an ambulatory aid for old people. Background: Many aged people use a bassinet as ambulatory aid. But the safety of using the bassinet as ambulatory aid has not been verified yet. Method: The 13 university-students who don't have musculoskeletal disorders volunteered to participate in this study. According to structural analysis of the both tools, we compared the structural stability of an outdoor rollator with the structural stability of a bassinet. And when the participants walked using both tools, the motions were captured and analysed. We measured the angle of shoulder joint and the angle of trunk from the ground when the participants were walking. And we found the distance from participants' pressure cone apex and greater trochanter. Results: Following the structural analysis, the bassinet has the lower structural stability than the outdoor rollator. When the people used the bassinet as ambulatory aid, the angle of the shoulder joint was bigger than to use the outdoor rollator. The angle of trunk wasn't different between the outdoor rollator and the bassinet. And distance from pressure cone apex to greater trochanter was far to use the bassinet than to use the outdoor rollator. Conclusion: Through the structure analysis and gait analysis of the bassinet and the outdoor rollator, we can be aware of that the bassinet has problem of stability. Therefore the people who use the bassinet as an ambulatory aid, especially supporting body weight, may be hurt due to the problems of stability. Application: This research can be used for developing a study of the ambulatory aid and preventing the accident when the aged people use the ambulatory aid.

• Wind and Structures
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• 제21권4호
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• pp.407-424
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• 2015

To explore the favorable structural system of cable-stayed bridges with ultra-kilometer main span, based on a fully self-anchored cable-stayed bridge with 1400 m main span, a partially earth-anchored cable-stayed bridge scheme with the same main span is designed. Numerical investigation on the dynamic characteristics, aerostatic and aerodynamic stability of both two bridge schemes is conducted, and the results are compared to those of a suspension bridge with similar main span, and considering from the aspect of wind stability, the feasibility of using partially earth-anchored cable-stayed bridge in super long-span bridges with ultra-kilometer main span is discussed. Moreover, the effects of structural design parameters including the length of earth-anchored girder, the number of auxiliary piers in side span, the height and width of girder, the tower height etc on the dynamic characteristics, aerostatic and aerodynamic stability of a partially earth-anchored cable-stayed bridge are analyzed, and their reasonable values are proposed. The results show that as compared to fully self-anchored cable-stayed bridge and suspension bridge with similar main span, the partially earth-anchored cable-stayed bridge has greater structural stiffness and better aerostatic and aerodynamic stability, and consequently becomes a favorable structural system for super long-span bridges with ultra-kilometer main span. The partially earth-anchored cable-stayed bridge can achieve greater stiffness and better wind stability under the cases of increasing the earth-anchored girder length, increasing the height and width of girder, setting several auxiliary piers in side span and increasing the tower height.

• 한국철도학회논문집
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• 제9권5호
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• pp.594-600
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• 2006

In this study, transient and quasi-static analysis were done for the evaluation of structural integrity of the platform screen door due to train wind pressure. Fluent 6.0 was used to calculate the train wind pressure, and Ansys 10.0 was used to evaluate the structural stability of platform screen door due to train wind pressure. Transient analysis was used to check the design requirements of platform screen door, and quasi-static analysis was introduced to save the calculating time and check quickly structural performances when compared to those of transient analysis. The results show that structural stability of the platform screen door under train wind pressure is proven and quasi-static analysis can quickly check the structural integrity of platform screen door.

• International Journal of Aerospace System Engineering
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• 제6권1호
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• pp.1-7
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• 2019

In the present study, structural safety and stability on the main wing and tail planes of the 1.2 ton WIG(Wing in Ground Effect) flight vehicle, which will be a high speed maritime transportation system for the next generation, was performed. The carbon-epoxy composite material was used in design of wing structure. The skin-spar with skin-stressed structural type was adopted for improvement of lightness and structural stability. As a design procedure for this study, the design load was estimated with maximum flight load. From static strength analysis results using finite element method of the commercial codes. From the stress analysis results of the main wing, it was confirmed that the upper skin structure between the second rib and the third rib was unstable for the buckling load. Therefore in order to solve this problem, three stiffeners at the buckled region were added. After design modification, even though the weight of the wing was a little bit heavier than the target weight, the structural safety and stability was satisfied for design requirements.

• Wind and Structures
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• 제20권1호
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• pp.95-115
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• 2015

Wind effects on roofs are usually considered by equivalent static wind loads based on the equivalence of displacement or internal force for structural design. However, for large-span spatial structures that are prone to dynamic instability under strong winds, such equivalent static wind loads may be inapplicable. The dynamic stability of spatial structures under unsteady wind forces is therefore studied in this paper. A new concept and its corresponding method for dynamic instability-aimed equivalent static wind loads are proposed for structural engineers. The method is applied in the dynamic stability design of an actual double-layer cylindrical reticulated shell under wind actions. An experimental-numerical method is adopted to study the dynamic stability of the shell and the dynamic instability originating from critical wind velocity. The dynamic instability-aimed equivalent static wind loads of the shell are obtained.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.195-202
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• 1999

This study present the stability of middle slabs directly supporting train loads in the subway station. According to results of Quality confirmation, mixing and curing conditions are good. But, when effects of hydration heat are analyzed, cracks seems to take place because tensile stress is higher than tensile strength in several points of middle slabs. It is found that vibration by train running don't have an effect on cracks in the structure. The structural analysis shows that there is no problem on the stability of structural body, but the design through 3-dimensional analysis is need to consider columns and opening specially in the subway station structures.

• Wind and Structures
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• 제29권1호
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• pp.15-32
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• 2019

Much advancement has been made in wind power due to modern technological developments. The wind energy technology is the world's fastest-growing energy option. More power can be generated from wind energy by the use of new design and techniques of wind energy machines. The geographical areas with suitable wind speed are more favorable and preferred for wind power deployment over other sources of energy generation. Today's wind turbines are mainly the horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs). HAWTs are commercially available in various sizes starting from a few kilowatts to multi-megawatts and are suitable for almost all applications, including both onshore and offshore deployment. On the other hand, VAWTs finds their places in small and residential wind applications. The objective of the present work is to review the technological development, available sizes, efficiencies, structural types, and structural stability of VAWTs. Structural stability and efficiencies of the VAWTS are found to be dependent on the structural shape and size.